Method and device for mounting a rotating member

ABSTRACT

A rotating anode is mounted on a shaft of an X-ray tube by means of a ring. The ring allows expansion and reduces the hyperstatic state of the assembly. The ring has the shape of a diabolo, preferably that of a hyperboloid structure generated by revolution. The ring dampens vibration phenomena in a shaft bearing the rotating anode and reduces noise-creating phenomena.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. application Ser.No. 10/825,512 filed Apr. 15, 2004, which is hereby incorporated byreference in its entirety, and claims the benefit of a priority under 35USC 119(a)-(d) to French Patent Application No. 03 50113 filed Apr. 17,2003, the entire contents of which are hereby incorporate by reference.

BACKGROUND OF THE INVENTION

The present invention is directed to a method and a device for mountinga rotating member. In particular, the present invention is directed to asource of radiation and, more particularly the mounting of a rotatinganode in an X-ray tube and a method for manufacturing a part of thisdevice. The rotating anode tubes are X-ray emitting tubes used mainly inmammography, although their use can be envisaged in other fields ofradiology, especially tomodensitometry. In mammography, the conditionsof the examination require the patient to place his or her breast on abreast-support tray. An X-ray emitting device, generally placed on avertical column that bears the breast-support tray, is placed close tothe patient's head. This proximity not only dictates particularly strictconstraints of electrical installation, but also requires that the X-raytube should not vibrate, so as not to inconvenience the patient duringan examination that moreover is a stressful experience. These vibrationsare noisy. In general, they are especially present as the sheathing ofthe tube is metallic and is itself sensitive to vibrations.

In practice, an X-ray tube with rotating anode has an anode rotating athigh speed. The anode is positioned so that, on one side, it faces acathode and, on the other, a window that is vacuum-tight but enables thepassage of the emitted X-rays. The rotation of the anode is prompted bya rotor working by means of bearings. The rotor drives the rotatinganode to which it is fixedly joined. Despite all the efforts made tobalance this rotating part, there are imbalances that contribute tomaking the entire tube vibrate. The shaft is fixed in the tube by beingfixed at both its ends. The shaft is thus fixed to a first structure,namely a first part of the sheathing of the tube, on one side and to asecond structure, namely a second part of the sheathing, on the otherside. The two structures are then linked to each other. If the linkingof the structures is rigid, such an assembly leads to a hyperstaticcondition in the holding of the shaft and, at a mechanical level, itentails breaks that are unacceptable. To overcome this drawback, one endof the shaft is mounted in a structure that is, in principle, thelightest and/or least rigid type of structure, using a ring that allowscertain degrees of freedom. The rings used, which generally have asquirrel-cage shape, are elastic but have the drawback of not beingreusable. Indeed, the rings are deformed because they have to beforce-fitted when mounted in a structure, before the insertion of ashaft end. Furthermore, the insertion of the rings themselves requiresan exertion of considerable force during assembly.

The value of the rings is that they resolve the problems related to thehyperstatic condition and furthermore allow the expansion caused by theheating of the anode. However, they do not resolve the problem ofvibrations, which continue to be a source of problems for the patientand may even lead to faulty precision in the radiological imagesacquired.

BRIEF DESCRIPTION OF THE INVENTION

An embodiment of the invention is directed to the problems of vibrationand the re-utilization of the rings. In an embodiment of the inventionthe rings are diabolo-shaped rings. The diabolo-shaped rings aresupported in a housing in the structures by means of end crowns. Theyhold the shaft inside the diabolo by means of a narrowed central part ofthe diabolo. In an embodiment by making the diabolos in an open shape,the ring can be adapted to the manufacturing tolerance values of thebores that receive the ends of the shaft. The insertion of the ringstherefore no longer necessitates any excessive force fitting. The ringscan consequently be re-utilized. In an embodiment of the invention thediabolo is hyperboloid shape.

An embodiment of the invention is directed to a method for making thediabolo-shaped rings so that the cost of their manufacture is reduced tothe minimum. In an embodiment of the method, the diabolo shape is ahyperboloid shape.

An embodiment of the invention is a device for mounting a rotating anodein an X-ray tube comprising, in a first structure, a bore, a ring housedin this bore, with one end of a shaft of the rotating anode inserted inthis ring, wherein the ring comprises a diabolo shape generated byrevolution about an axis of the shaft.

An embodiment of the invention is a method for the manufacture of adiabolo comprising: forming a diabolo from a cylinder; forming beams inone wall of the diabolo wherein the beams being could be inclined.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the invention will be understood more clearly from thefollowing description and the accompanying figures. The figures aregiven purely by way of an example and in no way restrict the scope ofthe invention. Of these figures:

FIG. 1 is a schematic view of the device for mounting a rotating anode;

FIGS. 2 to 6 exemplify the making of a hyperboloid structure generatedby revolution fulfilling the role of a diabolo;

FIGS. 7 to 9 illustrate the effects of the mounting of the diabolo inthe mounting device;

FIGS. 10 a to 10 e show dimensions of a hyperboloid diabolo;

FIG. 11 depicts a modified form of construction relating to that of FIG.2; and

FIG. 12 depicts a modified form of construction relating to that of FIG.1.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a device for mounting a rotating member such as an anode 1in an X-ray tube. The X-ray tube itself is not shown. The rotating anode1 is thus rigidly mounted on a motor-driven rotor (preferably abrushless electric motor) about a shaft 3. The shaft 3 is mounted, forexample rigidly, in a first fixed structure 4 and by means of the ring5, in a second structure 6. A rotor 2 and the rotating anode 1 rotateabout an axis of rotation 7 aligned with the shaft 3. In this example,the shaft 3 is rigidly fixed to the structure 4 by known means. Forexample, it is screwed into the structure with a screw. The structures 4and 6 are furthermore connected in the sheathing of the X-ray tube sothat they are fixed with respect to each other. In practice, one of thetwo structures, in this case the structure 4, is massive. The otherstructure, namely the structure 6, is lighter. In any case, thestructure 4 is less sensitive than the structure 6 to the vibratoryforces generating an acoustic source. This type of assembly gives riseto vibrations transmitted by the shaft 3 to the structure 6, which thensends out disturbing noises despite the presence of the ring 5.

In an embodiment of the invention, the ring 5 has a diabolo shapegenerated by revolution about an axis that is the axis 7 of the shaft 3.This shape is shown in FIGS. 5 and 6. Such an axis comprises a firstcrown 8 and a second crown 9, both circular and cylindrical, withgeneratrix lines parallel to the axis 7 of the shaft 3. These crowns 8and 9 are connected to each other by a set of beams that, in thisembodiment are inclined as shown at 10. It is possible however toprovide non-inclined beams but, as shall be seen here below, theinclination of the beams better ensures the integrity of the ring whenit is being used. The mounting of the diabolo between the shaft 3supporting the rotating elements and the structure 6 of the sheathing ofthe tube then gives the desired noise attenuation.

Several methods for manufacturing the diabolo-shaped ring of theinvention are possible. By way of example, dimensions and shapes of thering shall be specified with reference to FIGS. 10 a to 10 c. FIG. 2shows a plate 11, for example, a thin plate made of metal or an alloy,or even a composite material in which straight slots 12 are made,enabling the beams 13 to be individualized between each of the slots.The slots 12 and beams 13 are rectilinear, and in this example, they areoriented at right angles to the direction of two lintels 14 and 15 thatconnect the beams 13 to one another. The slots 12 can be cut out in thismanner by laser, matrix punching, etching or other similar methods.

Once the cutting-out operations have been performed, as shown in FIG. 3,a plate 11 is formed by making it turn about a circular cylindricalchuck oriented along an axis 16 parallel to the directions of the slots12 and of the beams 13. After shaping, the ends of the lintels 14 and 15can be soldered together so that the ring is closed. Herein below, anembodiment is described where the ring can be left open. Once thiscylinder is shaped, as seen in FIG. 4 a, the ring thus shaped is twistedby making the lintels 14 and 15, which are now circular, rotate incounter-rotational directions, 17 and 18 respectively, about an axis 19parallel to the directions of the slots 12 and beams 13. The structuresobtained are shown in FIGS. 5 and 6 in which the lintels 14 and 15occupy the places of the crowns 8 and 9 respectively. The twistingsolution is one solution but other equivalent techniques are possible.

For the making of an open ring, make an aperture 20 (FIG. 2) in alintel, for example, the lintel 15. This aperture can be made as aprolongation of a central slot 21. After shaping about the axis 16, theends 22 and 23 of the lintel 15 are joined together, for example bysoldering, while the corresponding ends of the lintel 14 are not joined.

Another procedure may comprise the use of a parallelogram-shaped plate24 rather than that of a rectangular plate 11. In this plate 24, theslots 25 are inclined, as also the beams 26, relative to the normal tothe lintels 14 and 15 (shown in FIG. 11). The plate 24 then undergoesthe same operation of shaping about a chuck with an axis 16perpendicular to the lintels 14 and 15. This leads to the making of acylindrical ring, shown in FIG. 4 b, in which the beams 26 are notoriented as the generatrix lines of the cylinder but are shaped in ahelix on the rim of the cylinder. Once this cylindrical ring isobtained, it can be stressed in a shaping mold. The mold on the wholehas the negative shape of the diabolo to be made, so that the beams 26are forced to bend towards the interior of the ring, in the direction ofthe axis 27 of the ring.

In one example, the inclination of the beams 26 on the lintels 14 and 15may be about 50° plus or minus 10°. The mold that receives the ring ofFIG. 4 b is a mold having a shape generated by revolution with an axisof revolution orthogonal to the directions of the lintels 14 and 15.

In another embodiment for making the diabolo, it is also possible tostart from a thick cylinder, for example with a thickness 28, as shownin FIG. 6. By lathing, it is then possible, in this thick cylinder, toobtain concavity by removing portions 29 from the diabolo, as alsoexcess thickness from the crowns 8 and 9, inside the diabolo. Once thisdiabolo is thus made, it is possible especially by laser cutting toindividualize the beams 10 between the crowns 8 and 9.

The molding method and the hollowing-out method do not necessarily leadto a hyperboloid diabolo. The twisting method leads to it naturally.

Whatever the method of manufacture used, it leads to the positioning ofbeams 10 inside the diabolo. These beams set up a narrowing of theavailable space within the diabolo while they are also attached, on bothsides of this diabolo, to elements having circumferences of greaterdiameter. To this effect, FIGS. 7 and 8 show the inner diameter of thediabolo, respectively before 30 and after 33 the insertion of the shaft3. In FIG. 8 especially, solid lines indicate the curves 31 of thesheaths of the beams 10 while dashes 32 indicate the same sheaths beforeinsertion. It is seen that the initial diameter 30 has widened to becomethe diameter 33 receiving the shaft 3. The differences of curvature 31and 32 constitute the elasticity that holds the end of the shaft 3 inthe structure 6 (FIG. 1).

FIG. 9 shows a diagram of forces, with a sinusoidal amplitude, occurringwhen the shaft 3 is subjected to radial forces. The distribution 34 ofthe stresses and their evaluation is such that it enables the thicknessof the ring 5, typically the thickness of the plate 11 or the plate 24,to be chosen. It also makes it possible to define the angles ofinclination of the beams 10 relative to axes 7, 19 or 27. It alsoenables the number of beams 13 to be defined. Finally, it enables thenature of the material, especially its Young's modulus, to be defined.These elements are furthermore determined as a function of the desireddifference in flexion, namely the difference between the curvatures 31and 32 or between the diameters 30 and 33.

FIGS. 10 a to 10 e show a particular embodiment of a ring having ahyperboloid shape. FIG. 10 b is a sectional view along the direction AAof FIG. 10 a, while FIG. 10 c is a sectional view along the directionBB. FIGS. 10 d and 10 e are views in perspective. All these figures showthat the ring has twenty slots and therefore twenty beams. This ringwhich, in one example, has been obtained by the third method described,has hyperboloid beams with a twist angle of 50°±5° as shown in FIG. 10e. The angle is measured in relation to an axis of revolution of thehyperboloid. In one example, the inner diameter of the ring is 7.6 mmwith a tolerance of 5/100^(th), the external diameter of the ring beingequal to 9.5 mm with a tolerance of 10/100^(th). FIG. 10 e shows thatthe twist angle may be 50°±5° relative to a plane perpendicular to theaxis of the shaft. FIG. 10 c shows that the slots have a width of 0.79mm, plus or minus 5/100 h mm, while the beams have a width of 0.7 mmplus or minus 5/100^(th) and a thickness of 0.5 mm plus or minus2/100^(th). In one example, the height of the ring is about 12 mm, plusor minus 5/100^(th); the height of the rings 8 and 9 formed from thelintels 14 and 15 being in the range of 1.5 mm plus or minus10/100^(th). The thickness of the plate can be, for example, between 0.3mm to 1.0 mm. Further, by way of example, the twist angle to form thehyperboloid ring may be less than or greater than 50° depending on thediameter reduction desired. For example, the twist angle can be about600 (low diameter reduction) or about 90° (high diameter reduction).

In the embodiment shown in FIG. 10 d the ring is open, especially at theposition of the slots and has a first aperture 34 formed in the lintel14. The aperture 34 is diametrically opposite to an aperture 35 formedin the lintel 15. The diametrical opposition is evaluated in relation tothe axis of revolution of the hyperboloid structure, which is not shownhere. Consequently, whatever the directions 36, as shown in FIG. 9, ofthe forces exerted on the shaft 3, the response of the ring will beidentical. There is no neglected direction, which is what would occurwith open rings.

The opening of the ring enables the insertion of the ring 5 into thebore 37 made in the structure 6. The narrowing of the aperture 34 and/orthe aperture 35 enables insertion and, furthermore, wedging.Furthermore, the narrowing makes it possible to accept a greatertolerance in the making of the bore that receives the end of the shaft 3in the structure 6.

As shown in FIG. 12, the embodiments make it is possible to obtain aparticularly simple longitudinal holding of the shaft 3, by making acavity 38 generated by revolution in this shaft 3 at the position thathas to receive the ring 5. This cavity 38 would have, for example, acurvature that is intermediate between the curvatures 31 and 32. If needbe, on the other side, in the rigid structure 4, it is also possible tomake another bearing with the same ring 39 to also hold the other end ofthe shaft 3 which, in this case too, would be provided with a cavitygenerated by revolution. In this case, especially with the cavities, acontrolled positioning of the shaft 3 would be obtained without any needto withstand longitudinal shifts.

As described an embodiment of the method may comprise: in a thin plate,cut-out slots are made, interposed with parallel beams, these parallelbeams being held together at their ends by lintels; the lintels and thebeams are shaped around a circular chuck with an axis perpendicular tothe lintels; and the circularly shaped lintels are twisted, with respectto each other, about an axis collinear with the axis of the chuck

As described an embodiment of the method may comprise: in a thin plate,cut-out slots are made, interposed with parallel beams, these parallelbeams being held together at their ends by lintels, the beams beinginclined in relation to a direction perpendicular to the lintels; thethin plate thus cut out is deformed by being forced into a mold with ashape generated by revolution, with an axis of revolution orthogonal tothe directions of the lintels; and the mold having an embossment in acentral part between the ends that receive the lintels.

One skilled in the art may make or propose various modifications to thestructure/way and/or function and/or result and/or steps of thedisclosed embodiments and equivalents thereof without departing from thescope and extant of the invention.

1. A method for the manufacture of a diabolo comprising: forming slotsin a plate, the slots being interposed with non-inclined parallel beams,the parallel beams being held together at their ends by lintels; shapingthe plate around a circular chuck with an axis perpendicular to thelintels; and twisting the circularly shaped lintels, with respect toeach other, about an axis collinear with the axis of the chuck toincline the beams.
 2. A method for the manufacture of a diabolocomprising: forming slots in a plate, the slots being interposed withparallel beams, the parallel beams being held together at their ends bylintels, the beams being inclined in relation to a directionperpendicular to the lintels; deforming the formed plate by being forcedinto a mold with a shape generated by revolution, with an axis ofrevolution orthogonal to the directions of the lintels; and the moldhaving an embossment in a central part between the ends that receive thelintels.
 3. The method according to claim 1 wherein the plate is aparallelogram.
 4. The method according to claim 2 wherein the plate is aparallelogram.
 5. The method according to claim 1 wherein the plate isrectangular.
 6. The method according to claim 1 wherein the formed slotsare straight between the lintels.
 7. The method according to claim 2wherein the formed slots are straight between the lintels.
 8. The methodaccording to claim 1 wherein the formed slots are rectilinear betweenthe lintels.
 9. The method according to claim 2 wherein the formed slotsare rectilinear between the lintels.
 10. The method according to claim 1wherein the formed slots are oriented at a right angle to the directionof the lintels.
 11. The method according to claim 2 wherein the formedslots are oriented at a right angle to the direction of the lintels. 12.The method according to claim 1 wherein an aperture is formed in atleast one diametrically opposite parts of the lintels.
 13. The methodaccording to claim 2 wherein an aperture is formed in at least onediametrically opposite parts of the lintels.
 14. The method according toclaim 1 wherein an aperture is formed in two diametrically opposed partsof the lintels.
 15. The method according to claim 2 wherein an apertureis formed in two diametrically opposed parts of the lintels.
 16. Amethod for the manufacture of a diabolo comprising: forming a diabolofrom a cylinder by removing portions of the cylinder; and forming beamsin a wall of the diabolo, the beams being inclined.
 17. The methodaccording to claim 1 wherein the inclination of the beams is about 50°relative to an axis of the diabolo.
 18. The method according to claim 2wherein the inclination of the beams is about 50° relative to an axis ofthe diabolo.
 19. The method according to claim 3 wherein the inclinationof the beams is about 50° relative to an axis of the diabolo.
 20. Themethod according to claim 5 wherein the inclination of the beams isabout 50° relative to an axis of the diabolo.
 21. The method accordingto claim 6 wherein the inclination of the beams is about 50° relative toan axis of the diabolo.
 22. The method according to claim 8 wherein theinclination of the beams is about 50° relative to an axis of thediabolo.
 23. The method according to claim 10 wherein the inclination ofthe beams is about 50° relative to an axis of the diabolo.
 24. Themethod according to claim 12 wherein the inclination of the beams isabout 50° relative to an axis of the diabolo.
 25. The method accordingto claim 14 wherein the inclination of the beams is about 50° relativeto an axis of the diabolo.
 26. The method according to claim 16 whereinthe inclination of the beams is about 50° relative to an axis of thediabolo.
 27. The method according to claim 17 wherein the inclination ofthe beams is 50°±10°.
 28. The method according to claim 17 wherein theinclination of the beams is 50°±5°.
 29. The method according to claim 1wherein the diabolo shape has twist angle greater than or less than 50°.30. The method according to claim 2 wherein the diabolo shape has twistangle greater than or less than 50°.
 31. The method according to claim16 wherein the diabolo shape has twist angle greater than or less than50°.
 32. method according to claim 1 wherein the diabolo has ahyperboloid shape.
 33. method according to claim 2 wherein the diabolohas a hyperboloid shape.
 34. method according to claim 16 wherein thediabolo has a hyperboloid shape.
 35. The method according to claim 32wherein the hyperboloid shape has an inner curvature diameter that isless than the initial diameter.